By Timothy Sparks
The philological evidence during the Koine period indicates that one can fornicate in marriage. For example, the root word πόρνη, porné (the Greek word translated into English as fornicator/ prostitute) is used in the LXX of Jer. 3:1 , 2, 3, 6, 7, 8, 9. Notice specifically in Jer. 3:8-9 both επόρνευσε (committed fornication/prostitution)[verse 8], πορνεία (fornication/prostitution) [verse 9] and εμοιχάτο (committed adultery) [verse 8], εμοίχευσε (she committed adultery) [verse 9] show that a married woman can commit both fornication and adultery. If a married person can become a πόρνη (prostitute) then a married person can commit πορνεία (fornication/ prostitution).
Hauck and Schulz in Theological Dictionary of the New Testament (Volume VI, page 587) state that during later Judaism (Apocrypha, Pseudepigrapha, Dead Sea Scrolls, Philo, Josephus, the Rabbis) “the use of πορνεία etc. gradually broadened as compared with the original usage. In the first instance πορνεία is mostly ‘harlotry,’ ‘extra-marital intercourse,’ . . . . Materially, however, it often means ‘adultery,’ cf. ἐν πορνείᾳ ἐμοιχεύθη, Sir. 23:23.” They give additional evidence as well from passages such as Sir. 23:16-27.
Here is the Greek text of Sirach 23:23 (also known as Ecclesiasticus 23:23)–πρῶτον μὲν γὰρ ἐν νόμῳ ὑψίστου ἠπείθησεν καὶ δεύτερον εἰς ἄνδρα αὐτῆς ἐπλημμέλησεν καὶ τὸ τρίτον ἐν πορνείᾳ ἐμοιχεύθη καὶ ἐξ ἀλλοτρίου ἀνδρὸς τέκνα παρέστησεν (http://en.katabiblon.com/us/index.php?text=LXX&book=Sir&ch=23)
English translations of Sirach 23:23 (also known as Ecclesiasticus 23:23):
22 So it is with a woman who leaves her husband
and presents him with an heir by another man.
23 For first of all, she has disobeyed the law of the Most High;
second, she has committed an offense against her husband;
and third, through her fornication she has committed adultery
and brought forth children by another man.
RSV For first of all, she has disobeyed the law of the Most High; second, she has committed an offense against her husband; and third, she has committed adultery through harlotry and brought forth children by another man.
22 The same is true of a woman who is unfaithful to her husband and presents him with a child by another man. 23 In the first place, she has broken the Law of the Most High. In the second place, she has wronged her husband. And in the third place, she has made a whore of herself by committing adultery and bearing the child of a man not her husband.
CEBA: “First, she’s disobeyed the Law of the Most High; second, she’s wronged her husband; third, she’s committed adultery by her illicit sexual behavior and produced children by another man” (http://www.biblestudytools.com/ceba/sirach/23.html).
KJV of Ecclesiasticus 23:22-23–
22 Thus shall it go also with the wife that leaveth her husband, and bringeth in an heir by another.
23 For first, she hath disobeyed the law of the most High; and secondly, she hath trespassed against her own husband; and thirdly, she hath played the whore in adultery, and brought children by another man.
See also: Do Only Single People Commit Fornication?